The human vertebral column consists of 32 to 35 vertebrae that form the spine of the body, and intervertebral discs that lie between adjacent vertebrae, wherein the vertebral column, i.e., the spine, forms the backbone of the trunk and communicates with the skull above and the pelvis below. The vertebrae include seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five sacral vertebrae, and three to five coccygeal vertebrae, wherein in adults, the five sacral vertebrae are fused to form one sacrum, and the three to five coccygeal vertebrae are fused to form one coccyx.
In general, the cervical spine is at top of the vertebral column and consists of seven vertebrae, wherein the cervical spine includes, beginning from the top, the first cervical vertebra, also called as the atlas, which has a rounded-shaped articular surface supporting the skull but does not have a vertebral body nor a spinous process; the second cervical vertebra, also called as the axis, which helps cervical rotation and has the odontoid process that rises perpendicularly from the vertebral body; the third to the sixth cervical vertebrae have small and wide vertebral bodies, triangular shaped vertebral foramens, and the spinous processes that are divided into two at each end thereof, and the seventh cervical vertebra, also called as the vertebra prominens, which has the spinous process without divided ends.
The cervical spine having the structure and function described above may be deformed or damaged by external shock from an accident, or due to long term bad posture. A cervical plate (a cervical fixing apparatus) having a plate and a screw is used to fix a damaged or deformed cervical spine, wherein the cervical plate (the cervical fixing apparatus) is fixedly inserted into the cervical spine. However, the cervical plate (the cervical fixing apparatus) is problematic in that after surgical procedure, frequent motions in the cervical spine leads to a back-out problem, which means the screw that is fixedly inserted into the cervical spine falls out by being loosed.
As a document of a related art, Korean Patent Application Publication No. 10-2011-0021142 (Published Mar. 4, 2011) discloses “Cervical Fixing Apparatus”.
To solve the back-out problem, the cervical fixing apparatus having a locking means has been proposed by the applicant of this invention. However, the cervical fixing apparatus is problematic in that the locking means accounts for most of the surface area of the plate, whereby it is difficult to bend the plate into a suitable shape for a patient's cervical spine during surgical procedure, and also makes it difficult to identify the surgical region within the plate with naked eye.